Error while submiting a form with nested fields

Error append with the djangoldp_invoicing module. Here is what I send to the server:

{
  "@context":"http://owl.openinitiative.com/oicontext.jsonld",
  "@graph":[
    {
    "@id":"./",
    "http://happy-dev.fr/owl/#batches":{"@id":"_:b381"},
    "http://happy-dev.fr/owl/#identifier":3,
    "http://happy-dev.fr/owl/#title":"Nouvelle facture",
    "http://happy-dev.fr/owl/#tvaRate":20
    },
    {
    "@id":"_:b381",
    "http://happy-dev.fr/owl/#tasks":{"@id":"_:b382"},
    "http://happy-dev.fr/owl/#title":"Batch 1"
    },
    {
    "@id":"_:b382",
    "http://happy-dev.fr/owl/#htAmount":1000,
    "http://happy-dev.fr/owl/#title":"Tache 1"
    }
  ]
}

Here is the response

AttributeError at /customer-invoices/
'ManyJsonLdRelatedField' object has no attribute 'child'

File "/usr/local/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "/usr/local/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/lib/python3.6/site-packages/django/views/decorators/csrf.py" in wrapped_view
  58.         return view_func(*args, **kwargs)

File "/usr/local/lib/python3.6/site-packages/rest_framework/viewsets.py" in view
  116.             return self.dispatch(request, *args, **kwargs)

File "/app/djangoldp/views.py" in dispatch
  135.         response = super(LDPViewSet, self).dispatch(request, *args, **kwargs)

File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py" in dispatch
  495.             response = self.handle_exception(exc)

File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py" in handle_exception
  455.             self.raise_uncaught_exception(exc)

File "/usr/local/lib/python3.6/site-packages/rest_framework/views.py" in dispatch
  492.             response = handler(request, *args, **kwargs)

File "/usr/local/lib/python3.6/site-packages/rest_framework/mixins.py" in create
  20.         serializer.is_valid(raise_exception=True)

File "/usr/local/lib/python3.6/site-packages/rest_framework/serializers.py" in is_valid
  236.                 self._validated_data = self.run_validation(self.initial_data)

File "/usr/local/lib/python3.6/site-packages/rest_framework/serializers.py" in run_validation
  434.         value = self.to_internal_value(data)

File "/usr/local/lib/python3.6/site-packages/rest_framework/serializers.py" in to_internal_value
  491.                 validated_value = field.run_validation(primitive_value)

File "/usr/local/lib/python3.6/site-packages/rest_framework/serializers.py" in run_validation
  626.         value = self.to_internal_value(data)

File "/app/djangoldp/serializers.py" in to_internal_value
  107.             return super().to_internal_value(data)

File "/app/djangoldp/serializers.py" in to_internal_value
  34.         return [self.child.to_internal_value(item) for item in data]

File "/app/djangoldp/serializers.py" in <listcomp>
  34.         return [self.child.to_internal_value(item) for item in data]

File "/app/djangoldp/serializers.py" in to_internal_value
  263.                             validated_value = field.run_validation(primitive_value)

File "/usr/local/lib/python3.6/site-packages/rest_framework/fields.py" in run_validation
  536.         value = self.to_internal_value(data)

File "/app/djangoldp/serializers.py" in to_internal_value
  34.         return [self.child.to_internal_value(item) for item in data]

File "/app/djangoldp/serializers.py" in <listcomp>
  34.         return [self.child.to_internal_value(item) for item in data]